Search for isospin-symmetry breaking in the A=62A=62 isovector triplet

The assignment of the first $2^+$ state in $^{62}$Ga has long been debated, due to its implications in triplet energy difference systematics in this mass region. An experiment has been performed at the IFIN-HH 9-MV Tandem accelerator using the ROSPHERE array in a mixed configuration of LaBr$_3$(Ce) and HPGe detectors, as well as an additional array of liquid scintillator neutron detectors. Excited states in $^{62}$Ga were populated through a $2n$ fusion-evaporation channel and an anisotropy ratio was obtained from neutron-filtered HPGe statistics of transitions observed at different angles. A $2^+$ state has been confirmed at an excitation energy of 978.1(1) keV. Theoretically, the interplay between isospin-symmetry breaking and shape-coexistence effects in the $A = 62$ isovector triplet is self-consistently treated within the beyond-mean-field complex excited Vampir variational model with symmetry projection before variation using an effective interaction obtained from a G matrix based on the charge-dependent Bonn CD potential adding the Coulomb interaction between the valence protons. Results are presented on Coulomb energy differences, mirror energy differences, triplet energy differences, and the superallowed Fermi $\beta$ decay of the ground state of $^{62}$Ge and $^{62}$Ga

Collective properties of neutron-deficient Nd isotopes: Lifetime measurements of the yrast states in 136^{136}Nd

International audienceLifetimes of the low-energy levels in Nd136, populated in the reaction Te124(O16,4n), were measured with the ROSPHERE array at the Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH), Bucharest-Magurele. The data were analyzed using the recoil distance Doppler shift method, and, in the cases where lifetimes were τ⩽1 ps, Doppler attenuation effects were taken into account. The deduced electromagnetic transition probabilities are discussed in the framework of the five-dimensional collective Hamiltonian (5DCH) theoretical model implemented with the D1S Gogny force, and detailed systematics of several observables in the even-even Nd isotopic chain are presented that highlight the transitional character of the neutron-deficient Nd isotopes. The 5DCH predictions are in overall good agreement with the present experimental results

Shape Coexistence at Zero Spin in 64Ni^{64}\mathrm{Ni} Driven by the Monopole Tensor Interaction

International audienceThe low-spin structure of the semimagic Ni64 nucleus has been considerably expanded: combining four experiments, several 0+ and 2+ excited states were identified below 4.5 MeV, and their properties established. The Monte Carlo shell model accounts for the results and unveils an unexpectedly complex landscape of coexisting shapes: a prolate 0+ excitation is located at a surprisingly high energy (3463 keV), with a collective 2+ state 286 keV above it, the first such observation in Ni isotopes. The evolution in excitation energy of the prolate minimum across the neutron N=40 subshell gap highlights the impact of the monopole interaction and its variation in strength with N